In the art directed to disposable syringes, it is known to provide a collapsable container for expressing medicines and the like through a needle, into humans or animals, for example. In my earlier U.S. Pat. No. 3,192,925, a previous development of mine set forth many of the parameters and utilities for devices of this type.
In administering medical injections it is frequently impossible to determine the precise location of the tip of the injection needle after it has been inserted into a patient. In many instances it is important to know whether the tip of the needle has lodged in a vein or an artery. In a conventional hypodermic syringe and needle, it has been a practice for some time for the person administering the injection to withdraw the plunger of the hypodermic syringe after the needle has been inserted into a patient to determine whether any blood wells up into the syringe. If the medication in the syringe is intended to be administered intravenously, the blood welling into the syringe indicates that the tip of the injection needle has lodged in a desired location-either an artery or a vein. If the intent was to deliver the medication into the muscle or subcutaneously, the person administering the injection would withdraw the injection needle and insert it into the patient in another location.
Prior Art disposable syringes are so constructed that it is not possible to create a negative pressure differential on the end of the injection needle to facilitate the withdraw of blood from the patient. In such syringes, the medication is expressed into the patient by squeezing a container which is configured much like the conventional toothpaste tube. Accordingly, it is not possible to manipulate the container itself to create a negative pressure within the container.